Method of detecting live microorganisms

Abstract

The invention relates to the field of optical biosensors and facilitates detection of mobile microorganisms in a liquid with a high degree of sensitivity even in the presence of a large number of brownian particles. The method in essence involves measuring, within a frequency range restricted at the lower end, the mean amplitude of the fluctuation in intensity of laser radiation scattered by the particles in the liquid, this being proportional to both the concentration and mobility of the particles. The turbidity of the liquid, which is proportional only to the particle concentration, is also measured and the presence of mobile microorganisms is assessed by comparing the two signals.

We claim: 
     
       1. A method for detecting live microorganisms, comprising passing laser radiation through the sample being analyzed and measuring the parameter characterizing the amplitude-frequency spectrum of fluctuation of the scattered laser radiation in the sample, simultaneously measuring the parameter characterizing the turbidity of the sample, while measuring the parameter characterizing the amplitude-frequency spectrum of fluctuation of scattered laser radiation with a restriction on the lower limit of the frequency range, and detecting the presence of live microorganisms by comparing the measured parameters. 
     
     
       2. The method as claimed in claim 1, wherein the lower limit of the frequency range is set taking account of the half-width of the Lorentz line. 
     
     
       3. The method as claimed in claim 1, further comprising calculating the derivatives of the measured parameters.